The field of the invention is inorganic chemistry and the present invention is particularly concerned with the preparation of basic copper phosphate.
The principles of preparing basic copper phosphate are known, as disclosed in GMELIN, Handbuch der anorg. Chemie, Vol. 60, Part A, p 175, and part B, pp 920-5, and H. Guerin & H. Kozicki, "Copper Orthophosphates", Chem. Abstracts, 47, 12086 (1953).
Recently copper(II) hydroxide phosphate of the composition Cu.sub.3 (PO.sub.4).sub.2.Cu(OH).sub.2 has become significant as a smoke-reducing additive for thermoplastics, in particular polyvinylchloride, as disclosed in U.S. Pat. No. 4,390,654, the disclosure of which is incorporated herein by reference.
The prior art methods for producing copper(II) hydroxide phosphate result, however, in products with a high grain size essentially exceeding ten microns and evincing a dark natural color.
Such properties, however, significantly reduce their application in colorless thermoplastics due to the definite coloration from the natural dark color and due to the inherently uneven distribution of the coarse powders.